The present invention pertains to improvements to an air conveyor of the type disclosed in U.S. patent application Ser. No. 08/062,939, filed May 13, 1993, assigned to the assignee of the present invention, issued on Aug. 1, 1995 as U.S. Pat. No. 5,437,521, and incorporated herein by reference. More particularly the present invention pertains to an air conveyor that conveys a stream of bottles along an input path and then selectively diverts bottles from the stream into one of two or more output paths.
An air conveyor is useful for the rapid transport of plastic bottles between work stations as, for example, between a storage station and a bottle-filling station. Typically, the known air conveyor includes a pair of flanges spaced to define an elongated slot between them, and a series of air ducts on opposite sides of the slot. Plastic bottles are formed with annular rims adjacent the tops of their necks. With the bottle necks extending through the slot and the rims overlying the spaced flanges, the bottles are suspended from the flanges and hang below the slot. Pressurized air from the ducts is directed in streams toward the bottles. The bottles move through the slot because of the force of the air streams against the bottles. Preferably, the bottles are conveyed in closely spaced succession.
In at least some of the conventional air conveyors, the air is directed through a plenum within a channel and against the tops of the bottles above their annular rims. This results in turbulence of air emerging through the elongated slot causing fluttering of the bottles and forward and backward wobbling as they are blown in the direction of bottle flow. Frequently, this wobbling will cause the bottles to wedge against one another.
The known air conveyors for plastic bottles are also deficient because once the bottles accumulate, the force of air required to move the slug (accumulated bottles) as a group must be high to overcome the drag. Therefore, the air pressure kept in the plenum is high enough to overcome the friction drag force of a slug should one occur. Consequently, as single or spaced bottles are conveyed by this high air pressure, their speed accelerates to a high velocity. This high acceleration and velocity is detrimental because the bottles collide at high speed with other bottles that have stopped or accumulated downstream potentially damaging the bottles. Conversely, if the force of air is reduced to prevent high acceleration of single bottles to prevent high speed impact, the reduced air flow will be inadequate to move the slugs (accumulated bottles).
In the prior art, much has been done in attempts to control the force of air to convey bottles at high speed yet avoid high speed impacts, such as modulation of the blower speed, which requires motor speed controls. However, reaction time in depleting the air stored in the plenum as well as in replenishing air blown within the plenum is rather slow compared to the more immediate response required in high speed production lines. In other prior art, louvers have been installed in the walls of the plenum in an effort to control the speed of single (random) bottles while applying greater force against the slugs. However, since accumulated slugs can and do occur randomly at any place along a given conveyor span, the complexity of such applications becomes neither economical nor practical.